Multi‐Temperature Pulsed Drying of Orange Slices in a Hybrid <scp>PVT</scp> Solar Dryer: Drying Kinetics, Moisture Diffusivity, and Economic Evaluation

Abstract

ABSTRACT This study evaluated a multi‐temperature pulsed hybrid photovoltaic/thermal (PVT) solar dryer for orange slices under staged drying temperatures of 60°C, 70°C, and 60°C combined with intermittent airflow operation of 60 s ON/60 s OFF. Drying experiments were conducted at Aswan University, Egypt, using orange slices with thicknesses of 3, 5, and 7 mm arranged at three vertical tray levels. The drying time increased with slice thickness and tray height, ranging from 9 to 12 h for 3 mm slices, 12 to 16 h for 5 mm slices, and 14 to 20 h for 7 mm slices, depending on tray position. Final moisture content decreased to 0.14–0.20 g water/g dry matter for 3 mm slices, while thicker slices showed higher residual moisture values. Effective moisture diffusivity ranged from 0.44 to 1.97 × 10 −11 m 2 /s and was influenced by both slice thickness and vertical tray location. Among the tested thin‐layer drying models, the Modified Midilli (II) model provided the best fit to the experimental moisture‐ratio data, with R 2 values of 0.9960–0.9989 and RMSE values of 0.0134–0.0186. Economic analysis showed that the 3 mm slice condition achieved the shortest payback period of 1.27 years, compared with 1.41 and 1.70 years for 5 and 7 mm slices, respectively. Overall, the results demonstrate that combining staged temperature control with pulsed airflow can improve drying performance, moisture‐transfer behavior, modeling accuracy, and economic feasibility in hybrid PVT solar drying of citrus slices.